CVE-2026-76070
Received Received - Intake

Stack-Based Buffer Overflow in Netis NC63 Firmware

Publication date: 2026-08-24

Last updated on: 2026-08-24

Assigner: VulnCheck

Description
Netis NC63 firmware through V3.0.0.3327 contains a stack-based buffer overflow vulnerability that allows unauthenticated remote attackers to overwrite saved stack state by submitting an oversized Base64-encoded password to the login handler in /bin/netis.cgi. Attackers can exploit the custom Base64 decoder's lack of output length validation against the fixed-size stack buffer to achieve remote code execution with root privileges, as the Boa web server executes the CGI environment as root.

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Meta Information

Published
2026-08-24
Last Modified
2026-08-24
Generated
2026-08-24
AI Q&A
2026-08-24
EPSS Evaluated
N/A
NVD
CVE-2026-76070
EUVD
EUVD-2026-64921

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
netis nc63 to 3.0.0.3327 (inc)
netis nc63 3.0.0.3327

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-121 A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Attack-Flow Graph

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Executive Summary

CVE-2026-76070 is a pre-authentication stack-based buffer overflow in the Netis NC63 router's firmware. It occurs in the /bin/netis.cgi login handler when a custom Base64 decoder writes decoded input into a fixed 64-byte stack buffer without validating the output length. Attackers can send a maliciously crafted Base64-encoded password exceeding 136 bytes to overwrite the saved return address, gaining control of the program counter and achieving remote code execution with root privileges.

Detection Guidance

To detect this vulnerability, scan for Netis NC63 devices running firmware version V3.0.0.3327 or earlier. Check for open ports 80 or 443 and test the /cgi-bin/login.cgi endpoint with a malformed Base64-encoded password payload to observe crashes or unexpected behavior.

Impact Analysis

This vulnerability allows unauthenticated remote attackers to execute arbitrary code on the router with root privileges. Potential impacts include unauthorized configuration changes, credential theft, network manipulation (DNS/firewall/routing), traffic redirection, service disruption, or full device compromise. Attackers could gain persistent access or use the router as a foothold into your network.

Compliance Impact

This vulnerability could lead to unauthorized access and control of network devices, potentially exposing sensitive data. For GDPR, it may result in unauthorized processing or access to personal data, violating principles of lawfulness and security. For HIPAA, it could compromise protected health information if the router is used in healthcare environments, violating safeguards for electronic protected health information.

Mitigation Strategies

Immediately update the Netis NC63 firmware to the latest version (V3.0.0.3889 or newer) from the official Netis website. If an update is unavailable, disable remote management access, block external access to the router's web interface, and consider replacing the device if no patch is provided.

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